Author Topic: Bessie, my first rebuild: 78 CB750F3 (Back on the road 2016-05-12) (Read 70778 times)

Tintop · « **Reply #175 on:** May 31, 2011, 05:10:03 PM »

Take a plug wrench, and a spare set of clean plugs on your ride. If it fouls the 1st plugs you can still get home.

wohali · « **Reply #176 on:** May 31, 2011, 09:59:36 PM »

I may have made my own trouble with the smoke. Opened the oil tank today and it was nearly overflowing. Using a pipette (think piece of 1/2" tubing and a thumb) I removed ~500cc before the level dropped to the top of the "XXXX" part of the dipstick!

Started her up and rode her around the block for about 1.5 miles. I now observe:

1. With rpm below 4500 there is negligible smoke.
2. At 4500-5000 she smokes significantly. I didn't dare go higher.
3. The front caliper needs to be bled before I take her out any further. One of the two calipers (right) has a broken bleeder I was unable to drill out, the Delta drill press wobbles too much for it. Trying some targeted rotated caliper resting overnight, hope to get the last bubble or two out that way.
4. After warming up, holding throttle around 3000 or so, suddenly I would get burst of fuel. She'd try to "tug tug tug" until I pulled in the clutch and went down to 2000-2500. This wasn't consistent though. I'm hoping syncing the carbs will solve this, I've already pulled apart all 4 carbs and cleaned them thoroughly, even the press-fit slow jets.
5. Carb #2 is slowly leaking out the bottom again. I'll either epoxy the hole closed or use a simple hose cutoff clamp at this point. I'm leaning towards the latter so I can drain the bowl if I want still.
6. The fuel tank cap vent seems to be plugged. I temporarily removed the rubber seal on the cap to compensate. I can blow through the hole in the top and feel it come out of the sides, but it takes a lot of effort, probably too much for the vacuum created by the carbs to overcome. Funny, I cleaned out the vent hole when I polished it, but it may need more TLC to open up further. Or maybe I got some compound in there...
7. Left turn idiot indicator came unplugged, 2 minute fix :-)

So I'm guardedly optimistic now. I don't know if time will stop smoking at higher RPMs or if something is still amiss...thoughts and suggestions welcome.

Flying J · « **Reply #177 on:** June 01, 2011, 07:30:15 PM »

For you caliper i hear you can soak them in..........cant remember.... but its an acid that eats metal but not aluminum. So you can soak them in there and it will eat away the bleeder. Then just clean paint and put in a new one.
Ill try and remember.

Flying J · « **Reply #178 on:** June 01, 2011, 07:35:19 PM »

Found it, Aluminum Sulphate.
have a read at this
http://forums.sohc4.net/index.php?topic=78937.0

brandEn · « **Reply #179 on:** June 01, 2011, 08:24:09 PM »

Also, for the bleeder if you haven't already tried a screw extractor or "EZ Out" give that a shot.

wohali · « **Reply #180 on:** June 02, 2011, 11:12:42 PM »

Today's update:

1. Fixed the unplugged wire; left turn idiot light lights up again.
2. My horn came in. Hooked it up and now I have the "F" dual-tone horn vs. the "K" single horn. Much nicer and louder! Looks correct too.
3. Put the front right caliper (with the busted bleeder) back on, after having hung it in funny orientations for a day, and bled the left side. It's firmer up front, but still a bit mushy, and sometimes requires a couple of pumps to really catch still. I feel it's safe enough to ride at faster speeds, for now. Also got a reference for a place in town that will drill out and thread in a new bleeder overnight; may hit them up next week.
4. Checked the oil level before starting her: YES again over full, this time by another 300cc. For those of you keeping track that means I filled her about 900cc over full with oil! No wonder she was smoking.
5. Rode her around the block a couple of times and got the tugging again....and a very small amount of smoking.
6. Installed a clamp on the bowl drain hose on carb #2 until I have time to get in there and epoxy the crack.
7. Synced the carbs. Compared to #2, all other 3 were very low on their vacuum. Gave them between 1/2 and 1-1/2 turns in at the top, and now they're all within 1 inHg of each other.
8. Rode it a few more times around the block - no more tugging, no more sudden acceleration. I think doing 6 and 7 above helped to resolve this issue.
9. Installed the vent line on the fuel tank.

So now I feel safe enough and stable enough to ride a bit farther away. I'm at about 3 miles since I rebuilt her - work has been busy - but this weekend I should be able to get out for a longer ride. Assuming the brakes feel good enough, I have no qualms about taking her thru the gears (but still not about 5k and not held at a single RPM for long). Probably won't risk the highway yet.

Keeping fingers crossed for the oil to stop burning!

wohali · « **Reply #181 on:** June 02, 2011, 11:16:12 PM »

@brandEn: Yup, tried an EZ out, and also tried drilling out. It's not budging. I think the PO used a standard hardened bolt, and it's not a bleeder in there. I also think it may not have been the right thread either.

@ffjmoore: Interesting chemistry. That would move the metals farther away on the electronegativity scale, leading to faster corrosion, but you'd have to keep scraping away the rust to get it to work, or the fluid wouldn't be in contact with new metal. (The rust would insulate the process.) I expect it'd take weeks if not months to fully rust out as well, even with a heated agitating wash bath. Faster to pay someone with a jig $30 to drill it out, yeah? Still I am a cheapskate

wohali · « **Reply #182 on:** June 02, 2011, 11:24:37 PM »

@ffjmoore: Ah I had the redox reaction wrong. Fascinating. I might give it a go! But I'll price the Aluminum Sulphate vs. the caliper place

It's a referral from the bike guy down the street so I am hoping I can get a deal

http://forums.sohc4.net/index.php?topic=38614.0

CafeDawg · « **Reply #183 on:** June 11, 2011, 11:00:52 AM »

Bump! So inquiring minds want to know....how's Bessie running? Still burning oil? Brakes fixed? Really hoping that everything is spot on, been following the build since I joined and she is one sweet resto.
Respect
CD

wohali · « **Reply #184 on:** June 12, 2011, 09:29:55 PM »

Update:

Brake got fixed; I got some help from a diamond Dremel bit to cut more out and re-centre the centre, then drilled out the centre. I got a brand new bleeder valve but it was leaking...turns out I probably drilled out the O-ring that was in the caliper, so I added a new one to the bottom of the bleeder valve and it stopped leaking entirely.

Rode Bessie for about 10 miles or so and the following things showed up:

1. Battery died at the end of my ride. I was able to kick start her at the gas station and get her home, but I think the regulator is misaligned. Going to pull and fix on the electronics bench, I don't trust "gapping" it when it's so easy to run a variable voltage through it and calibrate it properly.

2. Still burning oil, but at a far slower pace. After the ride I didn't see any appreciable drop in the oil amount, but it was enough that at one stop a lady in a car asked me what was wrong. I am really hoping the trend downwards will continue. Can anyone tell me if that's likely to happen or not? One interesting thing I did find out is that it seems less at speed, though I can't tell if it's just a constant amount getting through, making it look like that much less at speed.

3. I may or may not be not able to get into 5th gear. I was worried about the battery at the same time so I really can't tell. Once the charging circuit is working correctly I'll re-check. I know I could get her into 5th on the bench, so I am hoping I just mis-counted, or wasn't going fast enough to really get her into 5th properly. Worst case I live with revving high in 4th on the highway and find out what's wrong over next winterl best case, I mis-counted.

More soon...

wohali · « **Reply #185 on:** June 16, 2011, 11:22:21 AM »

Update! Got a lunchtime ride in...

1. Electrical problem was entirely my fault. I wired in the rectifier wrong. (hanging my head in shame, I have a Masters in EE...can't believe I did that

) I haven't done a formal charging test, but after riding her for 15 mins around 3-5k today, the starter motor sounded like it was getting more juice after the ride than before. Closing the case on this.

2. Still burning oil, though I'm only 20 miles into the rebuild. I'm noticing that when I put her away hot, the oil tank is full; when I go out to ride her after a few days, the tank is nearly empty. I'm betting the check valve in the oil pump has crud in it now, and the cylinders are partially flooded just sitting around. That said after 15 mins of riding I still am burning oil at stoplights, so who the hell knows. When I change the oil around 100 miles I guess I'll have to pull the pump and check it again. Here's hoping I can reuse that gasket.

3. I confirmed I can't get her into 5th gear. She comes out of 4th but 5th never connects. 1-4 are all fine, so I guess the shifter fork isn't completely fubar. I guess the first step is to pull the side cover and watch her shift, and spin the rear wheel on the centre stand to confirm she makes it into 5th gear. I'm hoping a pin is loose on the shifter drum or similar. I'm tempted to leave this until the winter, though; do you think I can survive on the highways in 4th alone? At least the redline on the F3 is high, but I'd be pushing her fairly hard at anything over 100kph/60mph.

4. New problem: won't idle below 2000 after getting warm, and choke kills the engine. That says "too rich" to me. First step: replacing the air filter, which I forgot to do while having her apart. If that doesn't solve it, I guess the carbs come off again...

Unhappy, a bit frustrated; tips welcome.

CafeDawg · « **Reply #186 on:** June 16, 2011, 11:43:28 AM »

Well sounds like a mixed bag. I'm no pro on this but my PO told me to check the oil hot because it settled when it hadn't been run. He suggested run for 15 min let sit for 5min and that would give you a better read. I just assumed this was part of the cold blooded nature of the SOHC4. Hopefully someone with more experience will chime in. I wouldn't be too worried, although I realize you are just breaking your engine in, as I recently had my F at 90mph in 4th gear and while I was Taching up I wasn't in the red yet. Good luck.
Respect
CD

wohali · « **Reply #187 on:** July 04, 2011, 09:07:44 PM »

So she's full up on the oil but still draining back in after sitting for a day or two. I will have to pull the pump again, I guess, and try and fix the check valve.

Still burning oil bad enough that I'm getting people honking at me to tell me about it, but the level is not going down appreciably at all. (I can't measure the difference). Head scratcher for sure.

Electrical system solid as a rock. Idling at 1250 and purring away at that. Seeing fouled plugs

GRock · « **Reply #188 on:** September 24, 2011, 08:20:59 PM »

So it's been a bit sense you last posted, what's Bessie doing?

wohali · « **Reply #189 on:** November 27, 2011, 12:48:50 PM »

After the rally, Bessie was benched for the remainder of the season. She had a lot of challenges from the rally - but she made it all the way there and back.

After all that kerfuffle with the rings, I'm going to have to overbore the pistons 0.25. There's no other way all of that oil is getting into the pistons, as near as I can tell. I will also have to double-check that the oil pump check valves are closing correctly, replace the ignition switch electrical connector, and possibly rip the bottom end back open to see why she can't get into fifth

All in all another busy winter, should help distract me from the dissertation I'm writing

grcamna2 · « **Reply #190 on:** November 29, 2011, 08:56:22 AM »

+1 on what CafeDawg said; I hope your oil pump check valve is O.K. once cleaned up.
I think you should just run it through the gears w/o lugging the engine or over revving it and that will smoothly break-in the new rings for you.I recommend just letting it spin as it wants to & down shift often while gently letting her wind up...varied rpm's w/ light torque loading of the internal parts...continually vary the rpms & 10wt30 is good break in oil to use.

wohali · « **Reply #191 on:** November 29, 2011, 06:10:34 PM »

She's been 1000 miles now on the new rings and the oil burning never got better. Every tank refill I have had to put in about 3/4L of oil.

She's going to get overbored to 0.25 with new larger rings and I think that's that

As much as it pains me to spend the money on that

grcamna2 · « **Reply #192 on:** November 29, 2011, 06:59:06 PM »

I recommend that you go a little bigger on the bore job...you may see it when you pull it down that the cyls. MAY be(I won't say they ARE)still slightly out-of-round.I have spoke w/ HondaMan on a similar problem & he told me that is a common problem on some older Honda's;when you pull it back apart, look into the cyls. & see if they were breaking-in evenly. I imagine you need a good break soon,huh??!

Sorry,but I haven't been following your progress through the complete project...;are you satisfied w/ all your valve guides & how they fit the valve stems & guide seals ?

Best Regards.

SOHC Digger · « **Reply #193 on:** March 04, 2012, 12:15:29 AM »

What's been going on lately?

calikid · « **Reply #194 on:** January 22, 2013, 02:59:07 PM »

i know were reviving from the dead but this was an amazing thread. Updates? Any tips for us rebuilding a 78' cb750f now that shes been up for a while?

Jerilee · « **Reply #195 on:** October 16, 2013, 02:47:09 PM »

Hi there! I read this thread some time ago between having my '78 and getting my '77 project. I had to come back again and give it another read. Amazing work, and so nice to see another woman on the board! : )

Did you ever get the engine woes sorted out? I hope it all turned out alright!

wohali · « **Reply #196 on:** October 18, 2013, 11:42:22 PM »

Hi everyone,

Thanks for the kind words during my absence. I'm out of work again and have time to look at the bike again. She currently has the following serious issues:

1. Burning oil. I have not yet pulled the pump to look at her, but at highway speeds she burns ~500-750mL per tank fill. This is totally unacceptable. For those who were asking about the extra rings in my group purchase, when I tear her back down, if the rings didn't set right and I can get by with another set of these, I will - otherwise, I'll release them for sale, I should have 2 or 3 sets left.

2. I can't get her to find fifth gear. After hitting fourth I literally cannot push her into fifth, and there is a bit of spring back when I try. I'm going to check the pins on the shifter but I expect I got a fork position wrong in the bottom end when matching the halves on reassembly. Tearing the bottom end back open again is going to be a messy and time consuming thing to have to do, but I'm not sure I have an alternative.

3. Chain problem. I had tightened the replacement front sprocket cover on a bit too tight, and the chain I put in was cracked on *every single link*. EEP! I put back on the old chain, fixed the mount on the sprocket cover and she runs fine, but it's way too loose of course. This is an easy weekend fix, but I need to get another 630 chain in.

4. Loose plug on the key cylinder would occasionally flake out in very hot weather and kill the bike. Some pressure on the back of the cylinder would bring her back. There's no sign of scorching or miswiring, it's just a bad connection, so this should just be a matter of ordering a new plug and wiring it in, or possibly a quick fix with some pliers. Still, not so nice.

5. A few cosmetic things would be nice to fix, and if I find spare money, I may find someone to build me a replacement 4-in-1, as the bottom front tube walls are starting to wear very thin.

Jerilee · « **Reply #197 on:** October 19, 2013, 02:47:00 AM »

Good luck with the fixes, especially the engine and transmission teardown. Keep us up to date on how it's going when you can.

Best of luck!

SOHC Digger · « **Reply #198 on:** October 21, 2013, 05:14:23 AM »

Glad to hear back from you! Sorry you're out of work, but I am a little jealous of the free bike time you have now!

wohali · « **Reply #199 on:** October 21, 2013, 09:09:47 PM »

I disassembled the shifter last night and it's not the shifter. My best guess is that I got M5 on backwards, or similar - so that 5th just doesn't engage. Oh well, that means I definitely need to get back into the bottom end now. More in a few days, I have guests from out of town I'm showing around the city this week.

News:

Author Topic: Bessie, my first rebuild: 78 CB750F3 (Back on the road 2016-05-12) (Read 70778 times)